[glib] build: Add #serial lines to m4 files

[Philip Withnall <pwithnall src gnome org>]

commit e130d2e511881041ecb6d956adb64ca9cabf2187
Author: Philip Withnall <withnall endlessm com>
Date:   Tue Oct 24 13:06:49 2017 +0100

    build: Add #serial lines to m4 files
    
    This helps prevent outdated copies of the m4 files being used if
    multiple copies are available in the search path.
    
    See https://www.gnu.org/software/automake/manual/html_node/Serials.html
    
    Signed-off-by: Philip Withnall <withnall endlessm com>
    
    https://bugzilla.gnome.org/show_bug.cgi?id=765552

 m4macros/glib-2.0.m4     |    3 +++
 m4macros/glib-gettext.m4 |    5 ++++-
 m4macros/glibtests.m4    |    3 +++
 m4macros/gsettings.m4    |    3 +++
 4 files changed, 13 insertions(+), 1 deletions(-)
---
diff --git a/m4macros/glib-2.0.m4 b/m4macros/glib-2.0.m4
index 23f6993..4b19019 100644
--- a/m4macros/glib-2.0.m4
+++ b/m4macros/glib-2.0.m4
@@ -1,6 +1,9 @@
 # Configure paths for GLIB
 # Owen Taylor     1997-2001
 
+# Increment this whenever this file is changed.
+#serial 1
+
 dnl AM_PATH_GLIB_2_0([MINIMUM-VERSION, [ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND [, MODULES]]]])
 dnl Test for GLIB, and define GLIB_CFLAGS and GLIB_LIBS, if gmodule, gobject,
 dnl gthread, or gio is specified in MODULES, pass to pkg-config
diff --git a/m4macros/glib-gettext.m4 b/m4macros/glib-gettext.m4
index dc17a98..df6fbf0 100644
--- a/m4macros/glib-gettext.m4
+++ b/m4macros/glib-gettext.m4
@@ -25,7 +25,10 @@
 #
 # Modified to require ngettext
 # Matthias Clasen <mclasen redhat com> 08/06/2004
-#
+
+# Increment this whenever this file is changed.
+#serial 1
+
 # We need this here as well, since someone might use autoconf-2.5x
 # to configure GLib then an older version to configure a package
 # using AM_GLIB_GNU_GETTEXT
diff --git a/m4macros/glibtests.m4 b/m4macros/glibtests.m4
index 7d5920a..581726a 100644
--- a/m4macros/glibtests.m4
+++ b/m4macros/glibtests.m4
@@ -1,3 +1,6 @@
+# Increment this whenever this file is changed.
+#serial 1
+
 dnl GLIB_TESTS
 dnl
 
diff --git a/m4macros/gsettings.m4 b/m4macros/gsettings.m4
index 35ee5aa..03c16fb 100644
--- a/m4macros/gsettings.m4
+++ b/m4macros/gsettings.m4
@@ -1,3 +1,6 @@
+# Increment this whenever this file is changed.
+#serial 1
+
 dnl GLIB_GSETTINGS
 dnl Defines GSETTINGS_SCHEMAS_INSTALL which controls whether
 dnl the schema should be compiled